Ado Entity Best Practice

Question

I’m just working on this interesting thing with ADO.net entities and need your opinion. Often a solution would be created to provide a service (WCF or web service) to allow access to the DB via the entity framework, but I working on an application that runs internally and has domain access pretty much all the time. The question is if it’s good practice to create a data service for the application to interface from or could I go from the WPF application directly to the entity framework. What’s the best practice in this case and what are some of the pros’ and cons’ to the two different approach.

Answer 1

It really depends on the level of complexity and the required level of coupling/modularity. I think a good compromise would be to create a EF model in it's own library or the like with a simple level of abstraction. In that scenario if you chose to change the model to use an exposed service instead of direct access it shouldn't be a big deal to refactor existing code and the new service could utilize the existing library.

Answer 2

By using entity framework directly, do you mean that the WPF application would connect to the database, or that it would still use services but re-use the entities?

If it's the first approach, I tend to be against this because it means multiple clients connecting to the database, which a) is an additional security concern, b) could make it more expensive from a licensing perspective, and c) means you don't get the benefits of connection pooling. Databases are the most expensive things to scale so I'd try to design the solution to use services and reduce the pressure on the database. But there are times when it's appropriate. One thing I've noticed is that applications which do start out connecting directly tend to get refactored to go via a service later; it seldom happens the other way around. But it might also be a case of YAGNI.

If it's the second approach, I think that's fine. It's common for people looking at WCF to think "service oriented" - that is, there should be a strict contract between services and things shouldn't be shared. But a "multi-tier" application, which is only designed to have one client, is also a perfectly valid architecture and doesn't need to be so decoupled. In that case, reusing the entities on both sides of the service boundary should be fine. However, I'm not sure how easy this is to do with EF specifically, since I haven't used it except in experiments.